The present invention is directed to a system and process for determining the effective value of a periodic signal.
It is known, that the effective value of a test signal can be determined digitally from samples of a periodic electric test signal using the following equation (1): ##EQU1##
See H. Germer and N. Wefers, Electronic Measurements, vol. 2, 2nd edition, 1990.
In this equation, I denotes the effective value of the periodic electric test signal, N denotes the number of samplings per period of the electric test signal and i(k) is the respective sample.
It is also known from the Germer and Wefers book that relatively large errors occur in determining the effective value of a periodic electric test signal when the duration of the sampling interval differs greatly from the period of the test signal. To nevertheless determine the effective value of a periodic electric test signal with a relatively high accuracy when there are differences between the duration of the sampling interval and the period of the test signal, German Patent DE 4,122,399 A1 discloses that the sampling interval can be shifted by one clock cycle with respect to the electric test signal, and corresponding effective values can then be determined from the resulting samples. The effective values thus obtained are used to calculate an average value, which gives the effective value of the test signal, regardless of frequency.